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Diagnostic Performance of Frequency-Domain Optical Coherence Tomography to Predict Functionally Significant Left Main Coronary Artery Stenosis

Diagnostic Performance of Frequency-Domain Optical Coherence Tomography to Predict Functionally... Hindawi Journal of Interventional Cardiology Volume 2021, Article ID 7108284, 10 pages https://doi.org/10.1155/2021/7108284 Research Article Diagnostic Performance of Frequency-Domain Optical Coherence Tomography to Predict Functionally Significant Left Main Coronary Artery Stenosis 1 1 1 2 Konstantina P. Bouki , Delia I. Vlad , Nikolaos Goulas , Vaia A. Lambadiari , 2 1 3 George D. Dimitriadis, Athanasios A. Kotsakis , Kyriaki Baroutsi , and Konstantinos P. Toutouzas 1 nd 2 Department of Cardiology, General Hospital of Nikea-Piraeus, Nikaia, Greece 2 nd 2 Department of Internal Medicine, University of Athens, Attikon Hospital, Athens, Greece Department of Medical Imaging, General Hospital of Nikea-Piraeus, Nikaia, Greece 4 st 1 Department of Cardiology, University of Athens, Hippokration Hospital, Athens, Greece Correspondence should be addressed to Delia I. Vlad; dr_deliavlad@yahoo.com Received 12 June 2021; Revised 9 September 2021; Accepted 22 October 2021; Published 15 November 2021 Academic Editor: Joseph Dens Copyright © 2021 Konstantina P. Bouki et al. ,is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Aims. ,e aim of this study was to assess the safety and diagnostic efficacy of frequency-domain optical coherence tomography (FD-OCT) in identifying functional severity of the left main coronary artery (LM) stenosis determined by fractional flow reserve (FFR). Methods and Results. 101 patients with LM lesion (20–70% diameter stenosis angiographically) underwent FFR mea- surement and FD-OCT imaging of the LM. ,e following parameters were measured by FD-OCT in the LM: reference lumen area (RLA), reference lumen diameter (RLD), minimum lumen area (MLA), minimum lumen diameter (MLD), % lumen area stenosis, and % diameter stenosis. ,e LM lesions were analyzable by FD-OCT in 88/101 (87.1%) patients. FFR at maximum hyperemia was ≤0.80 in 39/88 (44.3%) patients. FFR values were correlated significantly with FD-OCT-derived LM lumen parameters. An MLA cutoff value of 5.38 mm had the highest sensitivity and specificity of 82% and 81%, respectively, followed by an MLD of 2.43 mm (sensitivity 77%, specificity 72%) and AS of 60% (sensitivity 72%, specificity 72%) for predicting FFR<0.80. Conclusions. FD-OCT is a safe and feasible imaging technique for the assessment of LM stenosis. An FD-OCT-derived MLA of ≤5.38 mm strongly predicts the functional severity of an LM lesion. [2, 3]. In an effort to improve our diagnostic accuracy for the 1. Introduction evaluation of LM disease, several techniques have been used. Significant left main (LM) coronary artery disease (CAD) Fractional flow reserve (FFR) is the current standard has been considered a determinant of increased cardiac method for the functional assessment of a coronary lesion mortality approaching 50% at 3-year follow-up [1]. Because severity. It has been shown that an FFR value >0.80 predicts of its clinical significance, the accurate assessment of the a positive outcome for patients with LM disease and can be severity of an LM lesion is very important. Although cor- used as an accurate and safe criterion for postponing re- onary angiography has been accepted as the gold standard vascularization [3, 4]. However, an important limitation of for the evaluation of CAD, the severity of an LM stenosis is the LM FFR is the confounding effect of downstream ste- often underestimated or overestimated [2, 3]. Proximal nosis which are often present in patients with LM disease. location of the lesion, vessel tortuosity, overlap, or fore- Intravascular ultrasound (IVUS) has also been used in shortening are common limitations of the coronary angi- LM lesion assessment. A multicenter prospective study ography for the quantitative analysis of the LM stenosis showed that a minimum lumen area (MLA)>6 mm is a safe 2 Journal of Interventional Cardiology criterion to defer revascularization, while several other IVUS was made with the guiding catheter out of the LM. Stenosis studies [5–7] have proposed different cutoff values ranging was labeled as functionally significant if FFR ≤0,80. 2 2 from 4.5 mm to 7.5 mm . Fourier-Domain Optical Coherence Tomography (FD- 2.4. FD-OCT Imaging. After FFR assessment, FD-OCT OCT) provides high-resolution images of the coronary ar- imaging was performed using frequency-domain imaging teries allowing superior lumen border detection compared system (C7, St. Jude Medical, USA). 200 μg of intracoronary to IVUS [8–12]. ,e possibility of imaging the LM using nitroglycerin was administered before FD-OCT imaging to such a high-resolution imaging modality as FD-OCT is avoid coronary spasm. ,e LM was cannulated with a 6Fr attractive [13]. However, FD-OCT has the disadvantage of extra backup guiding catheter without side holes and at- the need for full blood displacement by contrast injection tention was paid to be in good alignment with the vessel. A during image acquisition, making difficult the imaging of 2.7 Fr FD-OCT imaging catheter (Dragonfly, St. Jude large vessels with proximal location such as LM. Recently, Medical, USA) was advanced over a conventional angio- Burzotta et al. [14, 15] showed that FD-OCT assessment of plasty guidewire distal to the LM bifurcation. FD-OCT nonostial segment of the LM is feasible. To date, no study has pullbacks were attempted from LAD or LCX according to evaluated the use of this imaging technique in the assessment the operator’s decision. Image acquisition was performed by of LM lesions in correlation with the FFR. an automated pullback with a speed of 20 mm/sec, while the ,e purpose of the present study was to assess the safety blood was removed by continuous manual injection of iso- and diagnostic efficacy of FD-OCT in identifying functional osmolar contrast (Iodixanol 370, Visipaque, GE Healthcare, severity of the LM stenosis determined by FFR. Ireland) through the guiding catheter. When the lesion was in the proximal part of the LM, to avoid the risk of masking, 2. Methods the guiding catheter was positioned just in front of the LM ostium or slightly disengaged during imaging acquisition. 2.1. Study Population. From May 2015 to January 2020, all ,e FD-OCT pullbacks were repeated until adequate visu- patients who underwent coronary angiography in General alization allowing quantitative assessment of the whole LM Hospital of Nikea and were found to have isolated LM segment was obtained. ,e required number of pullbacks stenosis (20%–70% diameter stenosis angiographically) were and the amount of injected contrast were calculated. All prospectively enrolled in the study. In all of these patients, images were stored digitally and analyzed offline by the FD- FFR measurement and FD-OCT imaging of the LM before OCTconsole. ,e acquisition run with the best image quality any intervention were attempted. Exclusion criteria were as was used for the offline analysis. follows: patients with LM stenosis >70% or <20%, patients with significant distal disease (left anterior descending artery (LAD) or left circumflex artery (LCX) stenosis ≥50%), acute 2.5. Angiographic Analysis. All angiograms were analyzed by myocardial infarction, abnormal regional wall motion of the an angiographer who was blinded to the clinical and FD- left ventricle, chronic kidney disease (serum creatinine OCT findings, using quantitative coronary angiographic >1.5 mg/dL), congestive heart failure, and known malignant (QCA) measurements. Quantitative coronary angiography disease. All demographic and clinical data were collected (QCA) was performed offline by a skilled analyzer using prospectively. standard commercial software (CAAS QCA 5, Pie Medical, All patients were informed, and written consent was Maastricht, Netherlands). ,e LM was divided into 3 seg- obtained for every patient. ments: the proximal 1/3 of the LM, the mid 1/3 of the LM, and the distal 1/3 of the LM. LM lesions were characterized as proximal if they were located in the proximal part of the 2.2. Cardiac Catheterization Procedure. Coronary angiog- LM. Reference lumen diameter (RLD), minimum lumen raphy was performed with the standard technique through diameter (MLD), percent diameter stenosis (% DS), length the femoral or the radial artery approaches, according to the of the whole LM (from the aortic orifice till the bifurcation of operator’s preference, using 6 Fr guiding catheters. All LAD and CX), and LM lesion length were determined by patients received 5.000–7.500 IU of unfractionated heparin QCA (Figure 1(a)). ,e QCA analysis was conducted from and intracoronary isosorbide dinitrate (0.2-0.3 mg) before the single-best-available projection with the least fore- angiography. shortening and the most severe stenosis. 2.3. FFR Measurement. Equalization was performed when 2.6. FD-OCT Imaging Analysis and Measurements. the guidewire sensor was positioned at the tip of the guiding FD-OCT images analysis was performed according to the catheter. After the equalization, a 0.014-inch pressure criteria of the International Working Group for Intravascular guidewire (St. Jude Medical, USA) was positioned ≥3 cm Optical Coherence Tomography Consensus Standards for distal to the LM in either the LAD, LCX, or both, depending Acquisition, Measurement, and Reporting of Intravascular Optical Coherence Tomography studies [16, 17]. All FD-OCT on which artery was least diseased distally. ,e FFR was measured during maximal hyperemia induced by intrave- images were analyzed by an experienced analyst who was blinded to the angiographic and FFR results. For the present nous infusion of adenosine at 140–280 μg/kg/min [7]. In patients with LM proximal stenosis, the FFR measurement study, quantitative FD-OCT analysis focused on the whole Journal of Interventional Cardiology 3 Figure 1: Example of proximal left main (LM) stenosis. (a) Angiographic view showing a proximal LM stenosis. ,e measurements of the LM length and the lesion length are also presented (double arrows). (b). Optical coherence tomography (FD-OCT) cross-sectional images of the LM with measured lumen dimensions. B1: reference lumen area (RLA); B2: minimum lumen area (MLA). (c) Longitudinal FD-OCT reconstruction of the LM showing the location of measurements (B1 and B2) and the measurements of the total LM length and the lesion length (double arrows). LM region from the catheter tip until the ostia of its bifur- An LM proximal lesion was considered analyzable cation branches (defined as the first cross-sectional image of (visible and measurable) by FD-OCT if 2 conditions were the daughter vessel where the other branch was not visible). satisfied: ,e LM was divided into 3 segments, proximal, mid, and (1) ,e total length of the LM measured by FD-OCT was distal, in accordance with the angiographic analysis. ,e equal to the total length of the LM measured by following parameters were measured from the cross-sectional angiography (differences smaller than 1 mm were images: reference lumen area (RLA), minimum lumen area considered negligible) (MLA), percent area stenosis (% AS), RLD, MLD, and % DS (2) ,e visualization of the proximal part of the LM was (Figure 1(b)). ,e length of the LM as well as the LM lesion optimal with less than 5 artifact frames length was measured from the long-axis view (Figure 1(c)). Frames with lumen border visibility less than 270 were In accordance to the above analysis, lesions located at the considered artifact and excluded from the analysis. Causes mid or distal part of the LM were considered analyzable by for artifact frames were recorded and classified as follows: FD-OCT if the visualization was optimal at the mid or distal portion of the image out of screen (because of eccentric segment of the LM with less than 5 artifact frames at each part. position of the FD-OCTcatheter or very large size of the LM) and inadequate blood clearance of the lumen. Acquisition runs with many artifact frames causing inability of mea- 2.7. Statistical Analysis. Data were analyzed using IBM SPSS surements were excluded from the analysis. Statistics version 23. Categorical variables were presented as 4 Journal of Interventional Cardiology counts and percentages. Normally distributed continuous proximal LM lesion, the total number of pullback runs variables were presented as mean values with standard (4.53± 0.81 versus 2.44± 1.06, p< 0.001, respectively) and the related contrast infused (47.43± 6.70 versus 26.28± 9.63, deviations; Shapiro-Wilk test was used to determine whether data were normally distributed. Comparisons between p< 0.001, respectively) were significantly higher than those categorical variables were done with x (Pearson’s chi-square in the patients with mid or distal LM stenosis. test). Comparisons between study groups were performed ,ere was a significant correlation between QCA and with t-test and correlations were tested by the Pearson FD-OCT measurements of the LM length (r � 0.698, correlation coefficient. Linear regression analysis was used to p< 0.001), RLD (r � 0.524, p< 0.001), MLD (r � 0.360, determine the correlation coefficients between FFR and FD- p � 0.001), and degree of % DS (r � 0.374, p< 0.001). OCT measurements and presented using scatter plot However, FD-OCT measured larger RLD, MLD, smaller % graphics. Receiver operating characteristic (ROC) curve DS, and shorter LM length compared to QCA (Table 2). analyses of MLA, MLD, and % AS in predicting a positive FFR (≤0.80) were performed. ,e area under the curve (AUC) of the ROC curves was estimated and used as the 3.3. Relation between FD-OCT Measurements and FFR. index of classification accuracy. Values of p< 0.05 were Table 3 shows the comparison of FD-OCT measurements considered statistically significant. between the ischemic (FFR ≤0.80) and the nonischemic (FFR >0.80) groups of patients. Among the 88 patients with analyzable lesions by FD-OCT, 39 patients (44.3%) had 3. Results significant stenosis based on FFR values (FFR of ≤0.80 at maximum hyperemia) (Table 3). ,ese lesions had longer 3.1. Baseline Clinical and Angiographic Characteristics. A lesion length, smaller RLA, smaller MLA, greater % AS, total of 128 patients were included in the study. In 18 pa- smaller MLD, and greater % DS by FD-OCT compared with tients, the operator did not perform FD-OCT imaging on the the lesions with an FFR >0.80 (Table 3). basis of anatomical characteristics, duration of the proce- ,ere was a significant correlation between FFR values dure, or patient discomfort. 9 patients out of 128 (7%) were and FD-OCT measurements of the MLA (R � 0.359, excluded because of inadequate quality of FD-OCT images. p< 0.001), MLD (R � 0.202, p< 0.001), and % AS Finally, 101 patients (60 male and 41 female) were pro- (R � 0.165, p< 0.001) (Figure 2). spectively enrolled in the study. Baseline clinical and an- Receiver operating characteristic curves for FD-OCT- giographic characteristics of the patients are shown in derived MLA, MLD, and % AS were used to predict func- Table 1. Among the 101 patients, 30 (29.7%) had a proximal tionally significant LM stenosis (Figure 3). An MLA cutoff lesion of the LM and 71 (70.3%) at the mid or distal segment. value of 5,38 mm had the highest sensitivity and specificity Most of the patients had de novo lesion of the LM (99/101 of 82% and 81%, respectively (AUC � 0.88, 95% CI: (98.0%) patients), with a mean % diameter stenosis of 0.80–0.95, p< 0.001), followed by an MLD of 2.43 mm 45.74± 11.3 by QCA. For the total of 101 lesions, the mean (sensitivity 77%, specificity 72%, AUC � 0.78, 95% CI: FFR value was 0.83± 0.07. 42 out of 101 (41.5%) patients had 0.68–0.88, p � 0.001) and % AS of 60% (sensitivity 72%, an FFR ≤0.80 (ischemic group). ,e ischemic group was specificity 72%, AUC � 0.79, 95% CI: 0.69–0.89, p< 0.001) found to have more severe LM stenosis (as it was expected) (Figure 3). and higher incidence of old myocardial infarction (Table 1). Among 41 lesions with an MLA of≤5.38 mm , 9 (22.0%) ROC analysis showed that a cutoff value of 50% angio- lesions had an FFR >0.80 (mismatch), while among 45 le- graphic stenosis by QCA could predict ischemic FFR with a sions with an MLA >5.38 mm , only 7 (15.5%) had an FFR sensitivity of 69.2% and a specificity of 65.3% (AUC � 0.66, ≤0.80 (reverse mismatch) (Figure 4). Additionally, taking a 95% CI � 0.54–0.78, p � 0.007). cutoff value of MLA ≤3.20 mm for prediction of ischemic FFR, only 1 out of 17 lesions (5.6%) with MLA ≤3.20 mm 3.2. FD-OCT Imaging Procedural Characteristics: Comparison had an FFR >0.80 (mismatch 5.6%). Meanwhile taking a between Angiographic and FD-OCT Measurements. cutoff value of MLA >6.76 mm for prediction of non- FD-OCTpullbacks were performed from LAD in 76 patients ischemic FFR, 0 out of 39 lesions (0%) with MLA>6.76 mm and from LCX in 25 patients. During flushing, 6 patients had an FFR ≤0.80 (reverse mismatch 0%). described chest pain. No patient had arrhythmias, cardiac Comparison between QCA (AUC � 0.66, 95% biomarker elevation, or contrast induced nephropathy. CI � 0.54–0.78, p � 0.007) and FD-OCTfor the prediction of ,e LM lesions were analyzable by FD-OCT in all pa- ischemic FFR (AUC � 0.88, 95% CI: 0.80–0.95, p< 0.001) tients (71/71 patients, (100%)) with mid or distal location of showed significant superiority of FD-OCTfor area under the the lesion. However, in patients with proximal location, the ROC curve (McNemar p � 0.013). lesion was analyzable by FD-OCT only in 17/30 (56.4%) patients. Subsequently, the final FD-OCT measurements were available in 88/101 (87.12%) patients. ,e deep position 3.4. Clinical Outcomes. ,ere were no complications of the guiding catheter into the LM was the most common during the diagnostic procedures. All the 42 patients in reason for the nonanalyzable LM proximal lesions (9/13 whom the FFR of the LM was ≤0.80 underwent revascu- cases (69.3%)), while the large number of artifact frames was larization with PCI successfully. No event occurred during a second reason (4/13 cases (30.7%)). In patients with hospitalization. Journal of Interventional Cardiology 5 Table 1: Baseline clinical and angiographic characteristics of the study population. Patients Patients FFR ≤0.80 FFR >0.80 Patients (n � 101) p value (n � (n � 42) 59) Baseline characteristics Age (years) 63.18± 9.8 62.38± 9.8 63.75± 9.8 0.493 Male, n (%) 60 (59.4) 24 (57.1) 36 (61.0) 0.696 Hypertension, n (%) 56 (55.4) 19 (45.2) 37 (62.7) 0.082 Diabetes, n (%) 34 (33.7) 18 (42.9) 16 (27.1) 0.099 Dyslipidemia, n (%) 76 (75.2) 30 (71.4) 46 (78.0) 0.453 Current smoker, n (%) 59 (58.4) 22 (52.4) 37 (62.7) 0.299 Family history, n (%) 45 (44.6) 14 (33.3) 31 (52.5) 0.056 LV ejection fraction (%) 50.45± 9.0 50.71± 7.9 50.25± 9.9 0.803 Acute coronary syndrome, n (%) 32 (31.7) 14 (33.3) 18 (30.5) 0.961 Prior myocardial infarction, n (%) 9 (9.0) 5 (12.0) 4 (6.8) 0.187 Prior coronary intervention, n (%) 49 (48.5) 24 (57.1) 125 (42.4) 0.143 Proximal lesion LM, n (%) 30 (29.7) 14 (33.3) 16 (27.1) 0.501 Angiographic characteristics Total LM length, mm 14.23± 5.2 15.13± 5.4 13.59± 4.9 0.142 LM lesion length, mm 3.09± 1.4 3.57± 1.4 2.73± 1.3 0.003 LM reference lumen diameter, mm 3.89± 0.7 3.92± 0.7 3.87± 0.6 0.677 LM minimum lumen diameter, mm 2.09± 0.5 1.94± 0.5 2.19± 0.4 0.010 LM % diameter stenosis 45.74± 11.3 50.22± 10.7 42.56± 10.6 0.001 Mean FFR value 0.83± 0.07 0.75± 0.02 0.89± 0.03 <0.001 Values are presented as n (%) or mean± standard deviation (SD). FFR � fractional flow reserve; LM � left main; LV � left ventricle. Table 2: Angiographic and optical coherence tomography measurements of the LM lesions. QCA (n � 88) FD-OCT (n � 88) p value LM length, mm 14.65± 5.3 12.48± 5.1 <0.001 Lesion length, mm 3.20± 1.5 3.72± 2.0 0.032 Reference lumen diameter, mm 3.79± 0.6 4.05± 0.6 <0.001 Minimum lumen diameter, mm 2.07± 0.5 2.46± 0.6 <0.001 Percent diameter stenosis (%) 44.78± 15.4 38.66± 14.4 <0.001 Reference lumen area, mm — 13.14± 4.1 Minimum lumen area, mm — 5.82± 2.9 Percent area stenosis (%) — 55.04± 18.7 Values are presented as n (%) or mean± standard deviation. FD-OCT �frequency-domain optical coherence tomography; LM � left main; n � number of patients; QCA � quantitative coronary angiography. Table 3: Comparison between optical coherence tomography measurements of LM stenosis with FFR ≤0.80 and FFR >0.80. FFR ≤0.80 (n � 39) FFR >0.80 (n � 49) p value LM length, mm 13.75± 4.9 11.47± 5.0 0.035 Lesion length, mm 4.29± 2.5 3.24± 1.5 0.020 Reference lumen diameter, mm 3.94± 0.5 4.10± 0.7 0.128 Minimum lumen diameter, mm 2.11± 0.4 2.74± 0.7 <0.001 Percent diameter stenosis (%) 45.32± 14.1 33.35± 12.4 <0.001 Reference lumen area, mm 11.86± 3.0 14.16± 4.6 0.008 Minimum lumen area, mm 3.96± 1.3 7.31± 3.0 <0.001 Percent area stenosis (%) 64.42± 17.6 47.58± 16.3 <0.001 Values are presented as n (%) or mean± standard deviation (SD). FFR � fractional flow reserve; LM � left main coronary artery; n � number of patients. between FD-OCT-derived MLA, MLD, and % AS with FFR 4. Discussion measurements. Among the different measured lumen pa- In the present study, we demonstrated that FD-OCT was rameters, MLA cutoff value of 5,38 mm provided the best safe and feasible for the evaluation of the LM lesions except sensitivity and specificity to predict the functional severity the proximal stenosis which were analyzable only in 56% of of the LM stenosis (82% and 81%, respectively, cases. We also found that there was a strong correlation AUC � 0.88). 6 Journal of Interventional Cardiology OCT AND FFR OCT AND FFR 0.95 (a) 0.95 (b) 0.90 0.90 0.85 0.85 0.80 0.80 0.75 0.75 R Linear = 0.359 R Linear = 0.202 p<0.001 p<0.001 0.70 0.70 2.00 4.00 6.00 8.00 10.00 12.00 1.00 1.50 2.00 2.50 3.00 3.50 4.00 MLA OCT MLD OCT OCT AND FFR 0.95 (c) 0.90 0.85 0.80 0.75 R Linear = 0.165 p<0.001 0.70 0.00 20.00 40.00 60.00 80.00 100.00 %AS Figure 2: Relation between optical coherence tomography (OCT) measurements and fractional flow reserve (FFR). (a) Relation between minimum lumen area (MLA) and FFR, (b) relation between minimum lumen diameter (MLD) and FFR, and (c) relation between percent area stenosis (% AS) and FFR. ,ere are few studies [13, 14, 18, 19] evaluating the proximal part of the LM as we found that only half (56%) of accuracy of FD-OCTfor the assessment of LM and there are the proximal LM lesions were analyzable by FD-OCT. even less concerning the ability of FD-OCT to image the However, this proportion was much higher than that proximal LM part [13, 19]. Burzotta et al. [14] excluded the suggested by previous studies. It is worth mentioning that ostial LM lesions and found that the LM bifurcation can be our study is the first prospective study dedicated to eval- perfectly evaluated by FD-OCT. Fujino et al. [19] con- uating the ability of OCT for the LM imaging. We used for firmed that FD-OCT assessment of the LM is feasible but the first time 2 predefined criteria for the LM visibility by the LM ostium was properly imaged only in 12.5% of FD-OCT: (1) the number of FD-OCTartifacts frames in LM patients. However, this study was a retrospective small should be less than 5 and (2) the total length of the LM study which was not dedicated to evaluating the LM by FD- measured by FD-OCT should be equal to the angiographic OCT. Recently, Roule et al. [13] found that overall more LM length. Consequently, the higher proportion of FD- than 90% of the quadrants of the LM were adequately OCT analyzable lesions at the proximal LM we found may assessable by FD-OCT, while most artifacts (18.6%) were be due to our different methodology. In this study guide, located at the proximal part of the LM. ,e present study extension catheter was not used during FD-OCT imaging. confirmed the difficulty of FD-OCT to evaluate the According to some reports, the use of this catheter might FFR FFR FFR Journal of Interventional Cardiology 7 ROC Curve ROC Curve MLA OCT MLD OCT 1.0 1.0 0.8 0.8 0.6 0.6 0.4 Cut off=5,38 mm2 0.4 Cut off=2,43 mm AUC=0.88 AUC=0.78 Sensitivity=82% Sensitivity=77% Specificity=81% Specificity=72% 0.2 0.2 0.0 0.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 1 – specificity 1 – specificity (a) (b) ROC Curve %AS OCT 1.0 0.8 0.6 Cut off=60% 0.4 AUC=0.79 Sensitivity=72% Specificity=72% 0.2 0.0 0.0 0.2 0.4 0.6 0.8 1.0 1 – specificity (c) Figure 3: Receiver operating characteristic (ROC) curves. (a–c) ROC curves for OCT-derived MLA, MLD, and % AS to predict FFR ≤0.80. ,e abbreviations are as in Figure 2. have improved the imaging of LM proximal lesions. Meanwhile, later, Dato et al. [21] using a combination of However, this remains to be tested in future studies. FD-OCT-derived parameters (% AS ≥70%, MLA ,ere are no data in the literature regarding FD-OCT- <2,5 mm , and plaque ulceration) demonstrated higher derived lumen parameters to predict the physiologic diagnostic accuracy with a sensitivity of 91% and a significance of an LM stenosis. However, the technique specificity of 93% for the prediction of an FFR <0.80 in has already been used to estimate the functional severity non-LM coronary artery lesions [15]. ,e same of coronary artery stenosis excluding LM lesions. In researchers more recently suggested that, in patients with particular, Gonzalo et al. [20] found an FD-OCT-derived intermediate distal LM disease, combination of different MLA <1.95 mm as the best cutoff value to predict FFR FD-OCT-derived parameters has the potential to select <0.80 with a sensitivity of 83% and a specificity of 63%. those patients in which revascularization can safely be Sensitivity Sensitivity Sensitivity 8 Journal of Interventional Cardiology OCT AND FFR standard in the evaluation of angiographic intermediate LM stenosis [26]. ,erefore, FFR measurement for intermediate LM 0.95 stenosis should be required to avoid unnecessary treatment. However, in cases of complex LM stenosis with additional 0.90 significant disease in the LAD and LCX, in which FFR may underestimate the lesion, an FD-OCT MLA of 5.38 mm can 0.85 help decision-making. Another issue that should be cleared is Mismatch that imaging of the LM proximal located stenosis was subop- timal by FD-OCTin half of the cases in our study. ,erefore, we 0.80 do not support the use of this technique for imaging proximal Reverse mismatch LM lesions. 0.75 4.1. Study Limitations. ,is study is a single-center study with a relatively small sample size. We excluded patients 0.70 with significant LAD or LCX stenosis which is a frequent 2.00 4.00 6.00 8.00 10.00 12.00 problem in everyday practice. We did not assess the clinical MLA OCT value of the FD-OCT-derived MLA <5,38 mm in decision- Figure 4: Scatter plot of FD-OCT MLA versus FFR values. ,e making for revascularization. Larger-scale studies are war- abbreviations are as in Figure 2. ranted to confirm the presented data and moreover clinical follow-up study with the new FD-OCT criterion. deferred [21]. However, the value of FD-OCT in the estimation of the functional severity of LM lesions re- 5. Conclusions mains unknown. FD-OCT was safe and feasible for the evaluation of the LM IVUS which is an older but well-established intra- lesions except the proximal LM lesions which were ana- coronary imaging technique has been used in several studies lyzable by FD-OCT in half of the cases. Among the ana- to evaluate the severity of the LM disease. Traditionally, an lyzable LM lesions, an FD-OCT-derived MLA ≤5.38 mm IVUS-derived MLA <6.0 mm is considered to represent was a useful criterion for the prediction of functional severity functionally significant LM stenosis. ,is strategy is based on of an LM stenosis. data from a number of observational studies. Jasti et al. found that an IVUS-derived MLA <5.9 mm strongly pre- dicts the physiological significance of an LM coronary 5.1. Impact on Daily Practice. FD-OCT is a safe and feasible stenosis [22]. In LITRO, a multicenter, prospective study [6], imaging technique for the assessment of LM stenosis except it was demonstrated that it is safe to defer revascularization if the proximal stenosis which is visible and analyzable in only the IVUS-derived MLA was≥6 mm . Smaller cutoff values of half of the cases. An FD-OCT-derived MLA ≤5.38 mm IVUS-derived MLA have been found in Asian patients with strongly predicts the functional severity of an LM lesion and generally smaller heart sizes [5, 7]. ,ese studies have can help towards the right clinical decision-making for the suggested that an IVUS-derived MLA of 4.5–4.8 mm may management of LM coronary artery disease. be the most appropriate. ,e LM MLA cutoff value of 5.38 mm identified by FD- Abbreviations OCT in our study was lower than IVUS-derived MLA of 6.0 mm used in current practice. However, this is in ac- AS: Area stenosis cordance with observations from previous studies [23–25] AUC: Area under the curve which have shown that FD-OCT estimates smaller vessel CAD: Coronary artery disease MLA compared to IVUS and the size of this discrepancy is CI: Confidence interval approximately 10%. Notably, the LM MLA cutoff value we DS: Diameter stenosis found by FD-OCT was also 10% lower than that of IVUS. FD- Frequency-domain optical coherence According to Bezerra et al. [25], possible explanations for OCT: tomography this size difference between FD-OCT and IVUS may be the FFR: Fractional flow reserve following: (1) better lumen discrimination by FD-OCT may IVUS: Intravascular ultrasound allow more accurate lumen visualization than IVUS, (2) LAD: Left anterior descending artery faster pullback of FD-OCT catheter may preclude selection LCX: Left circumflex artery of frames at maximum diastole, and (3) the smaller profile of LM: Left main coronary artery the FD-OCT catheter compared to IVUS may cause less MLA: Minimum lumen area stretch (Dotter effect) of the vessel in severe stenosis. MLD: Minimum lumen diameter Considering the prognostic impact of the identification of OR: Odds ratio significant LM stenosis and because the MLA cutoff value in our QCA: Quantitative coronary angiogram study showed a 25.6% rate of mismatch and 19.0% rate of RLA: Reference lumen area reverse mismatch, the decision-making cannot be relied on an RLD: Reference lumen diameter FD-OCT MLA alone. Until now, the FFR has been the gold ROC: Receiver operating characteristic curve. FFR Journal of Interventional Cardiology 9 arteries using three different software packages,” Euro- Data Availability Intervention, vol. 6, no. 3, pp. 371–379, 2010. [12] K. S. Rathod, S. M. Hamshere, D. A. Jones, and A. Mathur, ,e datasets used and/or analyzed during the current study “Intravascular ultrasound versus optical coherence tomog- are available from the corresponding author upon reason- raphy for coronary artery imaging—apples and oranges?” able request. Interventional Cardiology Review, vol. 10, no. 1, pp. 8–15, 2015. [13] V. Roule, I. Rebouh, A. Lemaitre et al., “Evaluation of left Conflicts of Interest main coronary artery using optical frequency domain imaging and its pitfalls,” Journal of Interventional Cardiology, ,e authors declare that there are no conflicts of interest. vol. 2020, Article ID 4817239, 7 pages, 2020. [14] F. Burzotta, I. Dato, C. Trani et al., “Frequency domain optical coherence tomography to assess non-ostial left main coronary Authors’ Contributions artery,” EuroIntervention, vol. 10, no. 9, pp. e1–e8, 2015. [15] F. Burzotta, R. Nerla, J. Hill et al., “Correlation between Dr. Konstantina P. Bouki and Dr. Delia I. Vlad contributed frequency-domain optical coherence tomography and frac- equally to this work. tional flow reserve in angiographically-intermediate coronary lesions,” International Journal of Cardiology, vol. 253, pp. 55–60, 2018. References [16] G. J. Tearney, E. Regar, T. 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Diagnostic Performance of Frequency-Domain Optical Coherence Tomography to Predict Functionally Significant Left Main Coronary Artery Stenosis

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Copyright © 2021 Konstantina P. Bouki et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Hindawi Journal of Interventional Cardiology Volume 2021, Article ID 7108284, 10 pages https://doi.org/10.1155/2021/7108284 Research Article Diagnostic Performance of Frequency-Domain Optical Coherence Tomography to Predict Functionally Significant Left Main Coronary Artery Stenosis 1 1 1 2 Konstantina P. Bouki , Delia I. Vlad , Nikolaos Goulas , Vaia A. Lambadiari , 2 1 3 George D. Dimitriadis, Athanasios A. Kotsakis , Kyriaki Baroutsi , and Konstantinos P. Toutouzas 1 nd 2 Department of Cardiology, General Hospital of Nikea-Piraeus, Nikaia, Greece 2 nd 2 Department of Internal Medicine, University of Athens, Attikon Hospital, Athens, Greece Department of Medical Imaging, General Hospital of Nikea-Piraeus, Nikaia, Greece 4 st 1 Department of Cardiology, University of Athens, Hippokration Hospital, Athens, Greece Correspondence should be addressed to Delia I. Vlad; dr_deliavlad@yahoo.com Received 12 June 2021; Revised 9 September 2021; Accepted 22 October 2021; Published 15 November 2021 Academic Editor: Joseph Dens Copyright © 2021 Konstantina P. Bouki et al. ,is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Aims. ,e aim of this study was to assess the safety and diagnostic efficacy of frequency-domain optical coherence tomography (FD-OCT) in identifying functional severity of the left main coronary artery (LM) stenosis determined by fractional flow reserve (FFR). Methods and Results. 101 patients with LM lesion (20–70% diameter stenosis angiographically) underwent FFR mea- surement and FD-OCT imaging of the LM. ,e following parameters were measured by FD-OCT in the LM: reference lumen area (RLA), reference lumen diameter (RLD), minimum lumen area (MLA), minimum lumen diameter (MLD), % lumen area stenosis, and % diameter stenosis. ,e LM lesions were analyzable by FD-OCT in 88/101 (87.1%) patients. FFR at maximum hyperemia was ≤0.80 in 39/88 (44.3%) patients. FFR values were correlated significantly with FD-OCT-derived LM lumen parameters. An MLA cutoff value of 5.38 mm had the highest sensitivity and specificity of 82% and 81%, respectively, followed by an MLD of 2.43 mm (sensitivity 77%, specificity 72%) and AS of 60% (sensitivity 72%, specificity 72%) for predicting FFR<0.80. Conclusions. FD-OCT is a safe and feasible imaging technique for the assessment of LM stenosis. An FD-OCT-derived MLA of ≤5.38 mm strongly predicts the functional severity of an LM lesion. [2, 3]. In an effort to improve our diagnostic accuracy for the 1. Introduction evaluation of LM disease, several techniques have been used. Significant left main (LM) coronary artery disease (CAD) Fractional flow reserve (FFR) is the current standard has been considered a determinant of increased cardiac method for the functional assessment of a coronary lesion mortality approaching 50% at 3-year follow-up [1]. Because severity. It has been shown that an FFR value >0.80 predicts of its clinical significance, the accurate assessment of the a positive outcome for patients with LM disease and can be severity of an LM lesion is very important. Although cor- used as an accurate and safe criterion for postponing re- onary angiography has been accepted as the gold standard vascularization [3, 4]. However, an important limitation of for the evaluation of CAD, the severity of an LM stenosis is the LM FFR is the confounding effect of downstream ste- often underestimated or overestimated [2, 3]. Proximal nosis which are often present in patients with LM disease. location of the lesion, vessel tortuosity, overlap, or fore- Intravascular ultrasound (IVUS) has also been used in shortening are common limitations of the coronary angi- LM lesion assessment. A multicenter prospective study ography for the quantitative analysis of the LM stenosis showed that a minimum lumen area (MLA)>6 mm is a safe 2 Journal of Interventional Cardiology criterion to defer revascularization, while several other IVUS was made with the guiding catheter out of the LM. Stenosis studies [5–7] have proposed different cutoff values ranging was labeled as functionally significant if FFR ≤0,80. 2 2 from 4.5 mm to 7.5 mm . Fourier-Domain Optical Coherence Tomography (FD- 2.4. FD-OCT Imaging. After FFR assessment, FD-OCT OCT) provides high-resolution images of the coronary ar- imaging was performed using frequency-domain imaging teries allowing superior lumen border detection compared system (C7, St. Jude Medical, USA). 200 μg of intracoronary to IVUS [8–12]. ,e possibility of imaging the LM using nitroglycerin was administered before FD-OCT imaging to such a high-resolution imaging modality as FD-OCT is avoid coronary spasm. ,e LM was cannulated with a 6Fr attractive [13]. However, FD-OCT has the disadvantage of extra backup guiding catheter without side holes and at- the need for full blood displacement by contrast injection tention was paid to be in good alignment with the vessel. A during image acquisition, making difficult the imaging of 2.7 Fr FD-OCT imaging catheter (Dragonfly, St. Jude large vessels with proximal location such as LM. Recently, Medical, USA) was advanced over a conventional angio- Burzotta et al. [14, 15] showed that FD-OCT assessment of plasty guidewire distal to the LM bifurcation. FD-OCT nonostial segment of the LM is feasible. To date, no study has pullbacks were attempted from LAD or LCX according to evaluated the use of this imaging technique in the assessment the operator’s decision. Image acquisition was performed by of LM lesions in correlation with the FFR. an automated pullback with a speed of 20 mm/sec, while the ,e purpose of the present study was to assess the safety blood was removed by continuous manual injection of iso- and diagnostic efficacy of FD-OCT in identifying functional osmolar contrast (Iodixanol 370, Visipaque, GE Healthcare, severity of the LM stenosis determined by FFR. Ireland) through the guiding catheter. When the lesion was in the proximal part of the LM, to avoid the risk of masking, 2. Methods the guiding catheter was positioned just in front of the LM ostium or slightly disengaged during imaging acquisition. 2.1. Study Population. From May 2015 to January 2020, all ,e FD-OCT pullbacks were repeated until adequate visu- patients who underwent coronary angiography in General alization allowing quantitative assessment of the whole LM Hospital of Nikea and were found to have isolated LM segment was obtained. ,e required number of pullbacks stenosis (20%–70% diameter stenosis angiographically) were and the amount of injected contrast were calculated. All prospectively enrolled in the study. In all of these patients, images were stored digitally and analyzed offline by the FD- FFR measurement and FD-OCT imaging of the LM before OCTconsole. ,e acquisition run with the best image quality any intervention were attempted. Exclusion criteria were as was used for the offline analysis. follows: patients with LM stenosis >70% or <20%, patients with significant distal disease (left anterior descending artery (LAD) or left circumflex artery (LCX) stenosis ≥50%), acute 2.5. Angiographic Analysis. All angiograms were analyzed by myocardial infarction, abnormal regional wall motion of the an angiographer who was blinded to the clinical and FD- left ventricle, chronic kidney disease (serum creatinine OCT findings, using quantitative coronary angiographic >1.5 mg/dL), congestive heart failure, and known malignant (QCA) measurements. Quantitative coronary angiography disease. All demographic and clinical data were collected (QCA) was performed offline by a skilled analyzer using prospectively. standard commercial software (CAAS QCA 5, Pie Medical, All patients were informed, and written consent was Maastricht, Netherlands). ,e LM was divided into 3 seg- obtained for every patient. ments: the proximal 1/3 of the LM, the mid 1/3 of the LM, and the distal 1/3 of the LM. LM lesions were characterized as proximal if they were located in the proximal part of the 2.2. Cardiac Catheterization Procedure. Coronary angiog- LM. Reference lumen diameter (RLD), minimum lumen raphy was performed with the standard technique through diameter (MLD), percent diameter stenosis (% DS), length the femoral or the radial artery approaches, according to the of the whole LM (from the aortic orifice till the bifurcation of operator’s preference, using 6 Fr guiding catheters. All LAD and CX), and LM lesion length were determined by patients received 5.000–7.500 IU of unfractionated heparin QCA (Figure 1(a)). ,e QCA analysis was conducted from and intracoronary isosorbide dinitrate (0.2-0.3 mg) before the single-best-available projection with the least fore- angiography. shortening and the most severe stenosis. 2.3. FFR Measurement. Equalization was performed when 2.6. FD-OCT Imaging Analysis and Measurements. the guidewire sensor was positioned at the tip of the guiding FD-OCT images analysis was performed according to the catheter. After the equalization, a 0.014-inch pressure criteria of the International Working Group for Intravascular guidewire (St. Jude Medical, USA) was positioned ≥3 cm Optical Coherence Tomography Consensus Standards for distal to the LM in either the LAD, LCX, or both, depending Acquisition, Measurement, and Reporting of Intravascular Optical Coherence Tomography studies [16, 17]. All FD-OCT on which artery was least diseased distally. ,e FFR was measured during maximal hyperemia induced by intrave- images were analyzed by an experienced analyst who was blinded to the angiographic and FFR results. For the present nous infusion of adenosine at 140–280 μg/kg/min [7]. In patients with LM proximal stenosis, the FFR measurement study, quantitative FD-OCT analysis focused on the whole Journal of Interventional Cardiology 3 Figure 1: Example of proximal left main (LM) stenosis. (a) Angiographic view showing a proximal LM stenosis. ,e measurements of the LM length and the lesion length are also presented (double arrows). (b). Optical coherence tomography (FD-OCT) cross-sectional images of the LM with measured lumen dimensions. B1: reference lumen area (RLA); B2: minimum lumen area (MLA). (c) Longitudinal FD-OCT reconstruction of the LM showing the location of measurements (B1 and B2) and the measurements of the total LM length and the lesion length (double arrows). LM region from the catheter tip until the ostia of its bifur- An LM proximal lesion was considered analyzable cation branches (defined as the first cross-sectional image of (visible and measurable) by FD-OCT if 2 conditions were the daughter vessel where the other branch was not visible). satisfied: ,e LM was divided into 3 segments, proximal, mid, and (1) ,e total length of the LM measured by FD-OCT was distal, in accordance with the angiographic analysis. ,e equal to the total length of the LM measured by following parameters were measured from the cross-sectional angiography (differences smaller than 1 mm were images: reference lumen area (RLA), minimum lumen area considered negligible) (MLA), percent area stenosis (% AS), RLD, MLD, and % DS (2) ,e visualization of the proximal part of the LM was (Figure 1(b)). ,e length of the LM as well as the LM lesion optimal with less than 5 artifact frames length was measured from the long-axis view (Figure 1(c)). Frames with lumen border visibility less than 270 were In accordance to the above analysis, lesions located at the considered artifact and excluded from the analysis. Causes mid or distal part of the LM were considered analyzable by for artifact frames were recorded and classified as follows: FD-OCT if the visualization was optimal at the mid or distal portion of the image out of screen (because of eccentric segment of the LM with less than 5 artifact frames at each part. position of the FD-OCTcatheter or very large size of the LM) and inadequate blood clearance of the lumen. Acquisition runs with many artifact frames causing inability of mea- 2.7. Statistical Analysis. Data were analyzed using IBM SPSS surements were excluded from the analysis. Statistics version 23. Categorical variables were presented as 4 Journal of Interventional Cardiology counts and percentages. Normally distributed continuous proximal LM lesion, the total number of pullback runs variables were presented as mean values with standard (4.53± 0.81 versus 2.44± 1.06, p< 0.001, respectively) and the related contrast infused (47.43± 6.70 versus 26.28± 9.63, deviations; Shapiro-Wilk test was used to determine whether data were normally distributed. Comparisons between p< 0.001, respectively) were significantly higher than those categorical variables were done with x (Pearson’s chi-square in the patients with mid or distal LM stenosis. test). Comparisons between study groups were performed ,ere was a significant correlation between QCA and with t-test and correlations were tested by the Pearson FD-OCT measurements of the LM length (r � 0.698, correlation coefficient. Linear regression analysis was used to p< 0.001), RLD (r � 0.524, p< 0.001), MLD (r � 0.360, determine the correlation coefficients between FFR and FD- p � 0.001), and degree of % DS (r � 0.374, p< 0.001). OCT measurements and presented using scatter plot However, FD-OCT measured larger RLD, MLD, smaller % graphics. Receiver operating characteristic (ROC) curve DS, and shorter LM length compared to QCA (Table 2). analyses of MLA, MLD, and % AS in predicting a positive FFR (≤0.80) were performed. ,e area under the curve (AUC) of the ROC curves was estimated and used as the 3.3. Relation between FD-OCT Measurements and FFR. index of classification accuracy. Values of p< 0.05 were Table 3 shows the comparison of FD-OCT measurements considered statistically significant. between the ischemic (FFR ≤0.80) and the nonischemic (FFR >0.80) groups of patients. Among the 88 patients with analyzable lesions by FD-OCT, 39 patients (44.3%) had 3. Results significant stenosis based on FFR values (FFR of ≤0.80 at maximum hyperemia) (Table 3). ,ese lesions had longer 3.1. Baseline Clinical and Angiographic Characteristics. A lesion length, smaller RLA, smaller MLA, greater % AS, total of 128 patients were included in the study. In 18 pa- smaller MLD, and greater % DS by FD-OCT compared with tients, the operator did not perform FD-OCT imaging on the the lesions with an FFR >0.80 (Table 3). basis of anatomical characteristics, duration of the proce- ,ere was a significant correlation between FFR values dure, or patient discomfort. 9 patients out of 128 (7%) were and FD-OCT measurements of the MLA (R � 0.359, excluded because of inadequate quality of FD-OCT images. p< 0.001), MLD (R � 0.202, p< 0.001), and % AS Finally, 101 patients (60 male and 41 female) were pro- (R � 0.165, p< 0.001) (Figure 2). spectively enrolled in the study. Baseline clinical and an- Receiver operating characteristic curves for FD-OCT- giographic characteristics of the patients are shown in derived MLA, MLD, and % AS were used to predict func- Table 1. Among the 101 patients, 30 (29.7%) had a proximal tionally significant LM stenosis (Figure 3). An MLA cutoff lesion of the LM and 71 (70.3%) at the mid or distal segment. value of 5,38 mm had the highest sensitivity and specificity Most of the patients had de novo lesion of the LM (99/101 of 82% and 81%, respectively (AUC � 0.88, 95% CI: (98.0%) patients), with a mean % diameter stenosis of 0.80–0.95, p< 0.001), followed by an MLD of 2.43 mm 45.74± 11.3 by QCA. For the total of 101 lesions, the mean (sensitivity 77%, specificity 72%, AUC � 0.78, 95% CI: FFR value was 0.83± 0.07. 42 out of 101 (41.5%) patients had 0.68–0.88, p � 0.001) and % AS of 60% (sensitivity 72%, an FFR ≤0.80 (ischemic group). ,e ischemic group was specificity 72%, AUC � 0.79, 95% CI: 0.69–0.89, p< 0.001) found to have more severe LM stenosis (as it was expected) (Figure 3). and higher incidence of old myocardial infarction (Table 1). Among 41 lesions with an MLA of≤5.38 mm , 9 (22.0%) ROC analysis showed that a cutoff value of 50% angio- lesions had an FFR >0.80 (mismatch), while among 45 le- graphic stenosis by QCA could predict ischemic FFR with a sions with an MLA >5.38 mm , only 7 (15.5%) had an FFR sensitivity of 69.2% and a specificity of 65.3% (AUC � 0.66, ≤0.80 (reverse mismatch) (Figure 4). Additionally, taking a 95% CI � 0.54–0.78, p � 0.007). cutoff value of MLA ≤3.20 mm for prediction of ischemic FFR, only 1 out of 17 lesions (5.6%) with MLA ≤3.20 mm 3.2. FD-OCT Imaging Procedural Characteristics: Comparison had an FFR >0.80 (mismatch 5.6%). Meanwhile taking a between Angiographic and FD-OCT Measurements. cutoff value of MLA >6.76 mm for prediction of non- FD-OCTpullbacks were performed from LAD in 76 patients ischemic FFR, 0 out of 39 lesions (0%) with MLA>6.76 mm and from LCX in 25 patients. During flushing, 6 patients had an FFR ≤0.80 (reverse mismatch 0%). described chest pain. No patient had arrhythmias, cardiac Comparison between QCA (AUC � 0.66, 95% biomarker elevation, or contrast induced nephropathy. CI � 0.54–0.78, p � 0.007) and FD-OCTfor the prediction of ,e LM lesions were analyzable by FD-OCT in all pa- ischemic FFR (AUC � 0.88, 95% CI: 0.80–0.95, p< 0.001) tients (71/71 patients, (100%)) with mid or distal location of showed significant superiority of FD-OCTfor area under the the lesion. However, in patients with proximal location, the ROC curve (McNemar p � 0.013). lesion was analyzable by FD-OCT only in 17/30 (56.4%) patients. Subsequently, the final FD-OCT measurements were available in 88/101 (87.12%) patients. ,e deep position 3.4. Clinical Outcomes. ,ere were no complications of the guiding catheter into the LM was the most common during the diagnostic procedures. All the 42 patients in reason for the nonanalyzable LM proximal lesions (9/13 whom the FFR of the LM was ≤0.80 underwent revascu- cases (69.3%)), while the large number of artifact frames was larization with PCI successfully. No event occurred during a second reason (4/13 cases (30.7%)). In patients with hospitalization. Journal of Interventional Cardiology 5 Table 1: Baseline clinical and angiographic characteristics of the study population. Patients Patients FFR ≤0.80 FFR >0.80 Patients (n � 101) p value (n � (n � 42) 59) Baseline characteristics Age (years) 63.18± 9.8 62.38± 9.8 63.75± 9.8 0.493 Male, n (%) 60 (59.4) 24 (57.1) 36 (61.0) 0.696 Hypertension, n (%) 56 (55.4) 19 (45.2) 37 (62.7) 0.082 Diabetes, n (%) 34 (33.7) 18 (42.9) 16 (27.1) 0.099 Dyslipidemia, n (%) 76 (75.2) 30 (71.4) 46 (78.0) 0.453 Current smoker, n (%) 59 (58.4) 22 (52.4) 37 (62.7) 0.299 Family history, n (%) 45 (44.6) 14 (33.3) 31 (52.5) 0.056 LV ejection fraction (%) 50.45± 9.0 50.71± 7.9 50.25± 9.9 0.803 Acute coronary syndrome, n (%) 32 (31.7) 14 (33.3) 18 (30.5) 0.961 Prior myocardial infarction, n (%) 9 (9.0) 5 (12.0) 4 (6.8) 0.187 Prior coronary intervention, n (%) 49 (48.5) 24 (57.1) 125 (42.4) 0.143 Proximal lesion LM, n (%) 30 (29.7) 14 (33.3) 16 (27.1) 0.501 Angiographic characteristics Total LM length, mm 14.23± 5.2 15.13± 5.4 13.59± 4.9 0.142 LM lesion length, mm 3.09± 1.4 3.57± 1.4 2.73± 1.3 0.003 LM reference lumen diameter, mm 3.89± 0.7 3.92± 0.7 3.87± 0.6 0.677 LM minimum lumen diameter, mm 2.09± 0.5 1.94± 0.5 2.19± 0.4 0.010 LM % diameter stenosis 45.74± 11.3 50.22± 10.7 42.56± 10.6 0.001 Mean FFR value 0.83± 0.07 0.75± 0.02 0.89± 0.03 <0.001 Values are presented as n (%) or mean± standard deviation (SD). FFR � fractional flow reserve; LM � left main; LV � left ventricle. Table 2: Angiographic and optical coherence tomography measurements of the LM lesions. QCA (n � 88) FD-OCT (n � 88) p value LM length, mm 14.65± 5.3 12.48± 5.1 <0.001 Lesion length, mm 3.20± 1.5 3.72± 2.0 0.032 Reference lumen diameter, mm 3.79± 0.6 4.05± 0.6 <0.001 Minimum lumen diameter, mm 2.07± 0.5 2.46± 0.6 <0.001 Percent diameter stenosis (%) 44.78± 15.4 38.66± 14.4 <0.001 Reference lumen area, mm — 13.14± 4.1 Minimum lumen area, mm — 5.82± 2.9 Percent area stenosis (%) — 55.04± 18.7 Values are presented as n (%) or mean± standard deviation. FD-OCT �frequency-domain optical coherence tomography; LM � left main; n � number of patients; QCA � quantitative coronary angiography. Table 3: Comparison between optical coherence tomography measurements of LM stenosis with FFR ≤0.80 and FFR >0.80. FFR ≤0.80 (n � 39) FFR >0.80 (n � 49) p value LM length, mm 13.75± 4.9 11.47± 5.0 0.035 Lesion length, mm 4.29± 2.5 3.24± 1.5 0.020 Reference lumen diameter, mm 3.94± 0.5 4.10± 0.7 0.128 Minimum lumen diameter, mm 2.11± 0.4 2.74± 0.7 <0.001 Percent diameter stenosis (%) 45.32± 14.1 33.35± 12.4 <0.001 Reference lumen area, mm 11.86± 3.0 14.16± 4.6 0.008 Minimum lumen area, mm 3.96± 1.3 7.31± 3.0 <0.001 Percent area stenosis (%) 64.42± 17.6 47.58± 16.3 <0.001 Values are presented as n (%) or mean± standard deviation (SD). FFR � fractional flow reserve; LM � left main coronary artery; n � number of patients. between FD-OCT-derived MLA, MLD, and % AS with FFR 4. Discussion measurements. Among the different measured lumen pa- In the present study, we demonstrated that FD-OCT was rameters, MLA cutoff value of 5,38 mm provided the best safe and feasible for the evaluation of the LM lesions except sensitivity and specificity to predict the functional severity the proximal stenosis which were analyzable only in 56% of of the LM stenosis (82% and 81%, respectively, cases. We also found that there was a strong correlation AUC � 0.88). 6 Journal of Interventional Cardiology OCT AND FFR OCT AND FFR 0.95 (a) 0.95 (b) 0.90 0.90 0.85 0.85 0.80 0.80 0.75 0.75 R Linear = 0.359 R Linear = 0.202 p<0.001 p<0.001 0.70 0.70 2.00 4.00 6.00 8.00 10.00 12.00 1.00 1.50 2.00 2.50 3.00 3.50 4.00 MLA OCT MLD OCT OCT AND FFR 0.95 (c) 0.90 0.85 0.80 0.75 R Linear = 0.165 p<0.001 0.70 0.00 20.00 40.00 60.00 80.00 100.00 %AS Figure 2: Relation between optical coherence tomography (OCT) measurements and fractional flow reserve (FFR). (a) Relation between minimum lumen area (MLA) and FFR, (b) relation between minimum lumen diameter (MLD) and FFR, and (c) relation between percent area stenosis (% AS) and FFR. ,ere are few studies [13, 14, 18, 19] evaluating the proximal part of the LM as we found that only half (56%) of accuracy of FD-OCTfor the assessment of LM and there are the proximal LM lesions were analyzable by FD-OCT. even less concerning the ability of FD-OCT to image the However, this proportion was much higher than that proximal LM part [13, 19]. Burzotta et al. [14] excluded the suggested by previous studies. It is worth mentioning that ostial LM lesions and found that the LM bifurcation can be our study is the first prospective study dedicated to eval- perfectly evaluated by FD-OCT. Fujino et al. [19] con- uating the ability of OCT for the LM imaging. We used for firmed that FD-OCT assessment of the LM is feasible but the first time 2 predefined criteria for the LM visibility by the LM ostium was properly imaged only in 12.5% of FD-OCT: (1) the number of FD-OCTartifacts frames in LM patients. However, this study was a retrospective small should be less than 5 and (2) the total length of the LM study which was not dedicated to evaluating the LM by FD- measured by FD-OCT should be equal to the angiographic OCT. Recently, Roule et al. [13] found that overall more LM length. Consequently, the higher proportion of FD- than 90% of the quadrants of the LM were adequately OCT analyzable lesions at the proximal LM we found may assessable by FD-OCT, while most artifacts (18.6%) were be due to our different methodology. In this study guide, located at the proximal part of the LM. ,e present study extension catheter was not used during FD-OCT imaging. confirmed the difficulty of FD-OCT to evaluate the According to some reports, the use of this catheter might FFR FFR FFR Journal of Interventional Cardiology 7 ROC Curve ROC Curve MLA OCT MLD OCT 1.0 1.0 0.8 0.8 0.6 0.6 0.4 Cut off=5,38 mm2 0.4 Cut off=2,43 mm AUC=0.88 AUC=0.78 Sensitivity=82% Sensitivity=77% Specificity=81% Specificity=72% 0.2 0.2 0.0 0.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 1 – specificity 1 – specificity (a) (b) ROC Curve %AS OCT 1.0 0.8 0.6 Cut off=60% 0.4 AUC=0.79 Sensitivity=72% Specificity=72% 0.2 0.0 0.0 0.2 0.4 0.6 0.8 1.0 1 – specificity (c) Figure 3: Receiver operating characteristic (ROC) curves. (a–c) ROC curves for OCT-derived MLA, MLD, and % AS to predict FFR ≤0.80. ,e abbreviations are as in Figure 2. have improved the imaging of LM proximal lesions. Meanwhile, later, Dato et al. [21] using a combination of However, this remains to be tested in future studies. FD-OCT-derived parameters (% AS ≥70%, MLA ,ere are no data in the literature regarding FD-OCT- <2,5 mm , and plaque ulceration) demonstrated higher derived lumen parameters to predict the physiologic diagnostic accuracy with a sensitivity of 91% and a significance of an LM stenosis. However, the technique specificity of 93% for the prediction of an FFR <0.80 in has already been used to estimate the functional severity non-LM coronary artery lesions [15]. ,e same of coronary artery stenosis excluding LM lesions. In researchers more recently suggested that, in patients with particular, Gonzalo et al. [20] found an FD-OCT-derived intermediate distal LM disease, combination of different MLA <1.95 mm as the best cutoff value to predict FFR FD-OCT-derived parameters has the potential to select <0.80 with a sensitivity of 83% and a specificity of 63%. those patients in which revascularization can safely be Sensitivity Sensitivity Sensitivity 8 Journal of Interventional Cardiology OCT AND FFR standard in the evaluation of angiographic intermediate LM stenosis [26]. ,erefore, FFR measurement for intermediate LM 0.95 stenosis should be required to avoid unnecessary treatment. However, in cases of complex LM stenosis with additional 0.90 significant disease in the LAD and LCX, in which FFR may underestimate the lesion, an FD-OCT MLA of 5.38 mm can 0.85 help decision-making. Another issue that should be cleared is Mismatch that imaging of the LM proximal located stenosis was subop- timal by FD-OCTin half of the cases in our study. ,erefore, we 0.80 do not support the use of this technique for imaging proximal Reverse mismatch LM lesions. 0.75 4.1. Study Limitations. ,is study is a single-center study with a relatively small sample size. We excluded patients 0.70 with significant LAD or LCX stenosis which is a frequent 2.00 4.00 6.00 8.00 10.00 12.00 problem in everyday practice. We did not assess the clinical MLA OCT value of the FD-OCT-derived MLA <5,38 mm in decision- Figure 4: Scatter plot of FD-OCT MLA versus FFR values. ,e making for revascularization. Larger-scale studies are war- abbreviations are as in Figure 2. ranted to confirm the presented data and moreover clinical follow-up study with the new FD-OCT criterion. deferred [21]. However, the value of FD-OCT in the estimation of the functional severity of LM lesions re- 5. Conclusions mains unknown. FD-OCT was safe and feasible for the evaluation of the LM IVUS which is an older but well-established intra- lesions except the proximal LM lesions which were ana- coronary imaging technique has been used in several studies lyzable by FD-OCT in half of the cases. Among the ana- to evaluate the severity of the LM disease. Traditionally, an lyzable LM lesions, an FD-OCT-derived MLA ≤5.38 mm IVUS-derived MLA <6.0 mm is considered to represent was a useful criterion for the prediction of functional severity functionally significant LM stenosis. ,is strategy is based on of an LM stenosis. data from a number of observational studies. Jasti et al. found that an IVUS-derived MLA <5.9 mm strongly pre- dicts the physiological significance of an LM coronary 5.1. Impact on Daily Practice. FD-OCT is a safe and feasible stenosis [22]. In LITRO, a multicenter, prospective study [6], imaging technique for the assessment of LM stenosis except it was demonstrated that it is safe to defer revascularization if the proximal stenosis which is visible and analyzable in only the IVUS-derived MLA was≥6 mm . Smaller cutoff values of half of the cases. An FD-OCT-derived MLA ≤5.38 mm IVUS-derived MLA have been found in Asian patients with strongly predicts the functional severity of an LM lesion and generally smaller heart sizes [5, 7]. ,ese studies have can help towards the right clinical decision-making for the suggested that an IVUS-derived MLA of 4.5–4.8 mm may management of LM coronary artery disease. be the most appropriate. ,e LM MLA cutoff value of 5.38 mm identified by FD- Abbreviations OCT in our study was lower than IVUS-derived MLA of 6.0 mm used in current practice. However, this is in ac- AS: Area stenosis cordance with observations from previous studies [23–25] AUC: Area under the curve which have shown that FD-OCT estimates smaller vessel CAD: Coronary artery disease MLA compared to IVUS and the size of this discrepancy is CI: Confidence interval approximately 10%. Notably, the LM MLA cutoff value we DS: Diameter stenosis found by FD-OCT was also 10% lower than that of IVUS. FD- Frequency-domain optical coherence According to Bezerra et al. [25], possible explanations for OCT: tomography this size difference between FD-OCT and IVUS may be the FFR: Fractional flow reserve following: (1) better lumen discrimination by FD-OCT may IVUS: Intravascular ultrasound allow more accurate lumen visualization than IVUS, (2) LAD: Left anterior descending artery faster pullback of FD-OCT catheter may preclude selection LCX: Left circumflex artery of frames at maximum diastole, and (3) the smaller profile of LM: Left main coronary artery the FD-OCT catheter compared to IVUS may cause less MLA: Minimum lumen area stretch (Dotter effect) of the vessel in severe stenosis. MLD: Minimum lumen diameter Considering the prognostic impact of the identification of OR: Odds ratio significant LM stenosis and because the MLA cutoff value in our QCA: Quantitative coronary angiogram study showed a 25.6% rate of mismatch and 19.0% rate of RLA: Reference lumen area reverse mismatch, the decision-making cannot be relied on an RLD: Reference lumen diameter FD-OCT MLA alone. Until now, the FFR has been the gold ROC: Receiver operating characteristic curve. FFR Journal of Interventional Cardiology 9 arteries using three different software packages,” Euro- Data Availability Intervention, vol. 6, no. 3, pp. 371–379, 2010. [12] K. S. Rathod, S. M. Hamshere, D. A. Jones, and A. Mathur, ,e datasets used and/or analyzed during the current study “Intravascular ultrasound versus optical coherence tomog- are available from the corresponding author upon reason- raphy for coronary artery imaging—apples and oranges?” able request. 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